Field of the Invention
The present invention elates to a magnetic recording medium which is preferably used in a magnetic recording and reproducing apparatus such as a hard disk drive, and a magnetic recording and reproducing apparatus including the magnetic recording medium.
Priority is claimed on Japanese Paten Application No. 2015-185500, filed on Sep. 18, 2015 and Japanese Patent Application No. 2016-038321, filed on Feb. 29, 2016, the contents of which are incorporated herein by reference.
Description of Related Art
In order to improve recording density of a magnetic recording and reproducing apparatus, a magnetic recording medium suitable for high recording density has been developed.
In the related art, examples of the magnetic recording medium include a magnetic recording medium in which a recording layer for recording information, a protective layer formed of carbon or the like, and a lubricant layer are formed on a substrate in this order. The protective layer protects the information recorded on the recording layer and increases slidability of a magnetic head. However, it is not possible to obtain sufficient durability of the magnetic recording medium only by disposing the protective layer on the recording layer.
For this reason, in general, the lubricant layer is formed by applying a lubricant onto the surface of the protective layer. By disposing a lubricant layer on the protective layer, it is possible to prevent the magnetic head of the magnetic recording and reproducing apparatus from being directly in contact with the protective layer, and to reduce a frictional force of the magnetic head sliding on the magnetic recording medium, and thus, durability is improved.
A perfluoropolyether-based lubricant, an aliphatic hydrocarbon-based lubricant, and the like have been proposed as the lubricant which is used in the magnetic recording medium.
For example, in Patent Document 1, a magnetic recording medium coated with a lubricant of perfluoroalkyl polyether (diol) having a structure of HOCH2—CF2O—(C2F4O)p-(CF2O)q-CH2OH (p and q are integers) is disclosed.
In Patent Document 2, a magnetic recording medium coated with a lubricant formed of perfluoroalkyl polyether (tetraol) having a structure of HOCH2CH(OH)—CH2OCH2CF2O—(C2F4O)p-(CF2O)q-CF2CH2OCH2—CH(OH)CH2OH (p and q are integers) is disclosed.
In Patent Document 3, a lubricant for a magnetic recording medium which has a perfluorooxy alkylene unit selected from —CF2O— or —CF2CF2O— and contains a phosphazene compound is disclosed.
In Patent Document 4, a magnetic recording medium including a lubricant layer in which a phosphazene compound and a compound having a perfluorooxy alkylene unit are mixed in a specific range is disclosed. In addition, in Patent Document 4, it is disclosed that the lubricant layer has a high bonding force with respect to the protective layer, and even in a case where the layer thickness of the protective layer decreases, a high coating ratio can be obtained.
In Patent Document 5, a lubricant containing a compound denoted by R1—C6H4O—CH2CH(OH)CH2OCH2—R2—CH2—O—R3 is disclosed.
In addition, outgas from siloxane-based organic Si which is used as a rubber seal for sealing the magnetic recording and reproducing apparatus is one of ionic contaminants on the magnetic recording medium. It is known that the outgas from the siloxane-based organic Si causes breakage or contamination of the magnetic head of the magnetic recording and reproducing apparatus (for example, refer to Patent Document 6).